Nowadays, touchscreen panel devices are widely used as input means. The touchscreen panel devices include a touchscreen panel sensor, a control circuit for detecting a contact position of an object on the touchscreen panel sensor, electrical interconnects, and a flexible printed circuit (FPC) board. In many cases, these touchscreen panel devices are used with a display device such as a liquid-crystal display or a plasma display, as the input means for the various types of hardware, for example, ticket-vending machines, automatic teller machines (ATMs), cell phones, or game consoles, that each incorporate such a display device. In such hardware, the touchscreen panel sensor is disposed over a display screen of the display device; therefore, the touchscreen panel device can perform highly direct data input into the display device. A region of the touchscreen panel sensor that faces a display region of the display device is transparent, and this region of the touchscreen panel sensor is to constitute an active area in which the sensor can detect the contact position (approach position).
The touchscreen panel devices can be divided into various types according to the principles of detecting the contact position or approach position of the object on the touchscreen panel sensor. Touchscreen panel devices of a capacitive coupling scheme are catching attention nowadays for reasons of optical brightness, design quality, structural simplicity, functional excellence, and the like. In the touchscreen panel devices of the capacitive coupling scheme, an external conductor (typically, finger) whose position is to be detected generates a new parasitic capacity by coming into contact or near-contact with the touch sensor through a dielectric. The touchscreen panel sensor utilizes a change in that capacitance to detect the position of the object on the sensor. The capacitive coupling scheme is subdivided into a surface type and a projected type. Of the two types, the projected type, in particular, is receiving attention for its suitableness for multitouch recognition (multipoint recognition) applications or requirements, as described in JP 2007-533044T.
Touchscreen panel sensors of the projected capacitive-coupling scheme include a dielectric, a first sensor electrode, and a second sensor electrode, the latter two sensor electrodes being formed in different patterns on both sides of the dielectric. Typically, the first sensor electrode and the second sensor electrode, both including a grid-like array of electrical conductors, detect a position of the electrical conductors based on an electromagnetic change or capacitance change that occurs when an external conductor (typically, a finger) comes into contact or near-contact with the touchscreen panel sensor.
As described in JP 1992-264613A, such a touchscreen panel sensor of the projected capacitive-coupling scheme is generally fabricated by bonding together via an adhesive layer, a first base film with a first sensor electrode formed thereupon, and a second base film with a second sensor electrode formed thereupon. In the thus-fabricated touchscreen panel sensor, the first sensor electrode and the second sensor electrode are connected to an external control circuit via electrical lead-out lines (electrical conductors for lead-out) formed in regions external to active areas of the respective base films. When the touchscreen panel device is used with a display device, the first sensor electrode and the second sensor electrode are formed from transparent electrically conductive materials of low electrical conductivity. On the other hand, the lead-out lines disposed outside the active areas do not need to be transparent and are each formed on the base film by screen-printing a metallic material of high electrical conductivity.                [Patent Document 1]: JP2007-533044T        [Patent Document 2]: JP1992-264613A        